ausblenden:
Schlagwörter:
East-asian monsoon; radiocarbon age calibration; mu us desert; late quaternary; pacific-ocean; paleoclimatic significance; atmospheric circulation; magnetic-susceptibility; accumulation rates; eolian deposition
Zusammenfassung:
The Chinese Loess Plateau (CLP) contains an extensive record of aeolian deposition through multiple glacial interglacial cycles. Independent chronologies based on pedostratigraphy, magnetic susceptibility, radiocarbon and luminescence dating were developed for 79 sites and used to estimate aeolian mass accumulation rates (MARS) for marine isotope stages 1-5. The regional median value of MAR for Stage 2 is 310 g/m(2)/yr compared to an estimate of 65 g/m(2)/yr for Stage 5. Estimated MARs from individual sites for Stage 2 are approximately 4.3 times greater than MARS for Stage 5 and 2.1 times greater than for Stage 1. MAR values at individual sites are consistently highest in the northwest and lowest in the southwest of the CLP during all marine isotope stages. MARs estimated on sections through loess terraces are consistently higher than MAR estimates at other sites, indicating that local recycling of loess material from exposed river valley deposits has been significant throughout the last 130 kyr. Although the spatial and temporal patterns in MAR are robust, there are uncertainties about the magnitude of these changes due to (a) lack of bulk density measurements and uncertainties in the chronologies for individual sites, (b) site and chronological biases in the sampling used to derive regional estimates, and (c) the unquantified nature of human impact on accumulation rates during the late Holocene. Nevertheless, the records from the CLP pose a number of challenges which could be addressed by numerical models of the palaeo-dust cycle. (C) 2003 Elsevier Ltd. All rights reserved.
